1. Field of the Invention
This invention is directed to regeneration of both amplitude and phase of optical binary phase shift-keying (BPSK) signals used in three areas: first, data communication by means of optical BPSK modulation format, second, data communication by means of optical quadrature phase shift-keying (QPSK) modulation format, wherein the BPSK signals constitute parts of the QPSK signals, and third, harmonically mode-locked lasers. In the BPSK signals the relative optical phase between the signals in adjacent time slots is either zero or π radians, while the signal amplitudes in all the time slots are the same. The invention is applied to, in particular though not exclusively, optical signals comprising optical return-to-zero (RZ) pulses. It has application to both 2R (re-amplification and reshaping) and 3R (re-amplification, re-shaping, and re-timing) regeneration.
2. Technical Background
Optical 2R (re-amplification and re-shaping) and 3R (re-amplification, re-shaping, and re-timing) regenerators have been disclosed in the following patents: U.S. patent application No. 20050180758 by Seguineau et al, U.S. patent application No. 20050078350 by Prucnal et al, U.S. patent application No. 20040208610 by Grosz et al, U.S. patent application No. 20040207906 by Dijaili et al, U.S. patent application No. 20040042800 by Lawrence, U.S. patent application No. 20040036946 by Webb et al, U.S. patent application No. 20040018020 by Chaput, U.S. patent application No. 20030190167 by Simon et al, U.S. patent application No. 20030043484 by Shen et al, U.S. patent application No. 20020191259 by Otani et al, U.S. patent application No. 20020080453 by Leuthold et al, U.S. patent application No. 20010022678 by Leclerc et al, U.S. Pat. No. 6,067,180 by Roberts, U.S. Pat. No. 5,798,852 by Billes et al, U.S. Pat. No. 5,513,030 by Epworth, U.S. Pat. No. 5,353,146 by Webb, U.S. Pat. No. 5,781,326 by Chiaroni et al. All of the aforementioned patent applications and patents address optical regeneration of the amplitude of optical signal. However, these inventions are not able of regenerating relative optical phase of the transmitted signals. This type of regeneration is crucial for modern communication systems using phase shift-keying modulation format, for example, binary phase shift-keying, differential binary phase shift-keying, quadrature binary phase shift-keying, and differential quadrature binary phase shift-keying modulation formats. Consequently, the aforementioned inventions can not be used for regeneration of the phase shift-keying optical signals. Thus, there exists a demand for optical regenerator enabling regeneration of the phase of transmitted signal (along with its amplitude) in communication links.
The present invention enables simultaneous regeneration of optical phase and the amplitude of a transmitted signal.